1. Field of the Invention
The present invention relates to an ink set, and more specifically to an ink set which can be suitably used for printers for inkjet recording.
2. Discussion of the Related Art
Inkjet recording is a recording system for forming characters or images, comprising directly jetting ink droplets from very fine nozzles to a recording medium, and depositing the ink droplets on the recording medium. This system has some advantages such that not only the device shows excellent operability at a low level of noise, but also the coloration is facilitated and plain paper can be used as a recording medium. Therefore, this system has been widely used in recent years.
In the inkjet recording, there have been recently used an ink set comprising inks having different colors with each other, such as black ink, yellow ink, cyan ink and magenta ink. However, bleeding has been sometimes generated at the boundaries between their inks at their contacted portions (hereinafter simply referred to as bleeding) when the inks having different colors are contacted with each other on a recording member before drying.
As ink sets in which bleeding is controlled, there have been proposed an ink set comprising an acidic black ink comprising an acidic carbon black, a basic surfactant and a water-soluble organic solvent, and a basic color ink (Japanese Patent Laid-Open No. Hei 9-183224); an ink set comprising a black ink containing a self-dispersible carbon black in which a hydrophilic group is bonded directly or via other atomic group to the surface of the carbon black, and a color ink containing a colorant having a reverse polarity to a colorant of the black ink (Japanese Patent Laid-Open No. Hei 10-140064); and the like.
However, when these ink sets are used, while the printout shows excellent bleeding resistance (difficulty in generation of bleeding, hereinafter referred to the same), there arise some defects such that the inks are aggregated by the contact of these inks with each other on the face or in the jetting outlet for the inks of the printer during inkjetting or cleaning of the printer head, so that nozzle clogging is caused, that jetting failure of the inks is caused, and that the linear jetting of the inks is inhibited, whereby crookedness (distortion) is generated.
Therefore, in order to eliminate these defects, it has been investigated to develop the jetting of inks having different ionicity with each other from separate heads. However, when this means is employed, there is a defect such that costs for producing an apparatus for this means highly increase because an apparatus used for this means should be compulsively large-scaled and becomes complicated.
An object of the present invention is to provide an ink set excellent in bleeding resistance, water resistance and rubbing resistance. Another object of the present invention is to provide an ink set which can be suitably used for inkjet recording, and which exhibits excellent jetting property, without changing the printer head in accordance with the kinds of the inks.
These and other objects of the present invention will be apparent from the following description.